The invention relates to a unitary connector, especially of thin sheet metal (preferably at most 4 mm thick per DIN 1052, and more preferably 2 to 3 mm thick depending on strength requirements), especially for substantially concealed connection of a held member (especially a joist) at the end face thereof to a holding member (especially a header), with a first flange to be applied against the end face of the held member to be connected and a second flange extending away therefrom and to be applied against the holding member, wherein these flanges or fastening flanges can each be provided with fastener openings (generally round), through which fasteners, such as nails, dowel pins, screws or bolts, can be driven into the members to be joined to one another.
Such L-shaped connectors are known from German Utility Model DE 29610381.0 U1 for at least substantially concealed connection of a held member at the end face thereof to a holding member. Such connections have proved to be very effective. Since cost and economy considerations provide constant motivation to minimize use of the necessary material, the thinnest possible material thickness that is adequate for the respective strength requirements is also desired for connectors of the cited class, since forming of sheet-metal blanks by folding up edges, bending, etc. becomes easier and thus more cost-effective with decreasing sheet-metal thickness.
It has nevertheless been found that the known connector could be further improved if it could be joined to the held member to be connected not only with its first flange but also with a third flange oriented perpendicular to the first flange and comprising an integral component of the connector, or, in other words, could have a T-shaped cross section, wherein the leg of the T is the first flange, one arm or web the second flange and the other arm or web the third flange. This third flange can also be labeled a tie strap, a connecting flange or a support flange.
In principle, it is certainly not difficult to make T-shaped connectors by cutting them, for example, from extruded sections having appropriate cross-sectional shape. On the other hand, it is obvious that several difficulties will arise in making them from thin sheet metal, since the desired third flange having sufficient strength could indeed be made from relatively thin sheet-metal material, because in installed condition it is subjected substantially only to tensile forces acting in its long direction, but the second flange obviously must have relatively high flexural strength.
An object of the present invention is therefore to improve the known connector of the class described in the introduction as regards the said aspects andxe2x80x94generally expressedxe2x80x94to provide a unitary connector of the cited class, which connector can indeed be made from relatively thin sheet metal (thickness preferably from about 2 to at most about 4 mm), but whose second flange nevertheless has adequate flexural strength to meet the strength requirements.
This object is achieved according to the present invention by the fact that the thickness of the second flange is doubled by folding the edge of the corresponding sheet-metal blank up or over at least one time along the rim of the second flange facing away from the held member to be connected, and thus giving it two-ply structure, as it were.
Although appropriate tests have shown that the aforesaid two-ply or multi-ply structure of portions of the connector which are subjected to relatively large stresses and strains (especially of bending nature) in the installed condition is generally already sufficient, it can be advantageous, in order to increase the resisting torque and thus the strength compared with a single-ply structure of thin sheet metal, if at least one free rimxe2x80x94particularly the rim of the connector adjacent the angle between the first and second flangesxe2x80x94is joined to the portion of the connector disposed there below or/and thereabove, as can be expediently achieved if necessary by welding in particular and, in fact, in particularly simple manner by spot welding wherever possible.
Another embodiment with the same objective is to join to one anotherxe2x80x94at one place at leastxe2x80x94parallel portions of the connector which are in contact with one another, as can also be achieved by welding (along the rims or by means of spot welds) or by adhesive bonding.
In the most preferred embodiment of the connector according to the present invention, at least one ply of the second flange is elongated in the direction of the held member to be connected, beyond the first flange, to form a third flange, which if necessary can engage in an appropriate slot of the held member to be connected, but in general rests expediently on the upper side of the held member to be connected and is fastened there. Since this third flange substantially has only the function of a tie strap, meaning that in installed condition under load it is subjected to stress and strain substantially only by tensile forces oriented in its long direction, it can of course be thinner as a rule than, for example, the second flange, and thus generally has only single-ply structure.
To ensure that the third flange does not have to be hammered or similarly treated for the first time during installation in order to form it such that its underside facing the first flange rests flush on the held member to be connected, the third flange adjacent the first flange can be disposed or formed in a manner offset in the direction of the first flange such that its underside is substantially aligned with the underside of the second flange, as will be further explained hereinafter on the basis of a practical example with reference to FIG. 1 of the drawing as shown in phantom lines.
Preferably, the fastener openings of at least one flange are formed at least partly such that they constitute an oblique forced guide known in the art for the respective fasteners to be driven through; the central axes of the respective fasteners are oriented such that they not perpendicular to the flange in question or its bearing surface, as will also be further illustrated hereinafter with reference to the drawing (see, for example, FIGS. 4, 8 and 12).
To achieve a further increase in flexural strength of the connector or of a portion of the connector, at least one flange can be reinforced by at least one molded crease or the like. For example, it has proved most advantageous if the second flange and/or the third flange is provided with at least one continuous crease facing away from the first flange.
For connectors which are subjected to greater stresses and strains but which, for the already cited reasons, must nevertheless be made from relatively thin sheet metal (preferably about 2 to 4 mm thick), it is also possible for all flanges to have at least two-ply structure if necessary.
In a further preferred embodiment of the present invention, the third flange acting as tie strap has single-ply structure, the first flange to be applied on the one end face of the held member to be connected has two-ply structure and the second flange, which is subjected to considerable bending stresses and strains, has three-ply structure (see, for example, FIGS. 9 to 12 and 13 to 16 of the drawings).
In a further preferred embodiment, the connector according to the present invention is provided, for the purpose of accommodating a rod-like fastener, such as a nail, dowel pin, screw or bolt, in the second flange, at least one first fastener opening, the longitudinal axis of which is aligned with the longitudinal axis of a second fastener opening (meaning that it coincides therewith or is identical thereto) associated with it and formed in the first flange.
In a further preferred embodiment, the connector according to the present invention is provided, for the purpose of accommodating a rod-like fastener, such as a nail, dowel pin, screw or bolt, in the third flange, at least one first fastener opening, the longitudinal axis of which is aligned with the longitudinal axis of a second fastener opening (meaning that it coincides therewith or is identical thereto) associated with it and formed in the first flange.
In the above mentioned first and second fastener openings, each associated in pairs with one another, each is dimensioned and arranged such that, in the finally installed condition of the connector, they bear interlockingly on the fastener they receive, while at the same time the angle formed by the two flanges so joined is endowed with stiffness by means of the rod-like fastener to be driven through them and traversing them after installation, the portion of the fastener extending between the two through openings in the installed condition then formingxe2x80x94in side viewxe2x80x94the hypotenuse of a right-angled triangle, which correspondingly stiffens the connector under load against relative bending of its flange and in factxe2x80x94in an appropriate embodimentxe2x80x94not only against bending but also against relative twisting.
In a preferred embodiment, there are provided in the flanges severalxe2x80x94depending on the dimensions of the connector on the one hand and on the dimensions of the members to be joined to one another on the other handxe2x80x94pairs of first and second fastener openings associated with one another, each for accommodation of one rod-like fastener.
The first and second fastener openings are preferably formed as round holes, since the function assigned thereto can hardly be achieved in general or at least is more difficult to achieve reliably with slots than is the case with holes.
Such an embodiment is advantageous especially if, as in a further preferred embodiment, the rod-like fastener for at least one pair of first and second fastener openings is a screw, wherein at least one fastener opening of the pair of fastener openings in question is provided with a female thread, which corresponds to the male thread of the screw. In a further preferred embodiment, both first and second fastener openings associated with one another can also be formed if necessary as threaded holes, so that the screw to be introduced into them during installation or screwed into them in the finally installed condition is held by thread engagement and therefore interlockingly in both first and second fastener openings.